An electric double layer capacitor generally employs a pair of polarizable electrodes that contain a porous matrix formed from conductive particles (e.g., activated carbon). The porous matrix is impregnated with a liquid electrolyte, which may be aqueous in nature. Due to the effective surface area of the porous material and the small spacing between the electrodes, large capacitance values may be achieved for the resulting capacitor. Nevertheless, one problem often associated with such capacitors is that the aqueous electrolyte tends to undergo thermal expansion when exposed to high temperature environments. This may cause leakage of the electrolyte from the capacitor, which may in turn lead to reduced capacitance and increased equivalent series resistance (“ESR”). As such, a need currently exists for an improved electric double layer capacitor that can exhibit good electrical performance, even when exposed to a high temperature environment.